feat (fabric-x): Make the Fabric-X application organization configurable

Fabric-X currently has several generated files that assume a specific application organization. Research how the application org identity is represented across crypto material, config files, policies, and runtime services.

Update the generator so the first application org from the shared Fablo config drives the Fabric-X output. The default config should still work, and a simple custom org/domain/MSP setup should also start successfully.

Start by tracing how the first application org in the shared Fablo config is consumed across generated crypto material, config files, policies, and runtime services. Verify the default configuration still works, then test a simple custom organization, domain, and MSP setup; done means both configurations start successfully.

Written by the indexing model from the issue text.